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35 .Nd "USB access library"
41 USB access library (libusb -lusb)
53 library contains interfaces for directly managing a usb device.
54 The current implementation supports v1.0 of the libusb API.
57 .Sh LIBRARY INITIALISATION / DEINITIALISATION
62 .Fn libusb_init libusb_context **ctx
63 This function initialises libusb. Must be called at the beginning
64 of the program. This function returns 0 on success or LIBUSB_ERROR on
70 .Fn libusb_exit "libusb_context *ctx"
71 Deinitialise libusb. Must be called at the end of the application.
76 .Fn libusb_strerror "int code"
77 Get ASCII representation of the error given by the
85 .Fn libusb_set_debug "libusb_context *ctx" "int level"
93 .Fn libusb_get_device_list "libusb_context *ctx" "libusb_device ***list"
96 the list of usb device available. All the device created by this
97 function must be unref and free when you are done with them. This
98 function returns the number of devices in list or a LIBUSB_ERROR code.
103 .Fn libusb_free_device_list "libusb_device **list" "int unref_devices"
104 Free the list of devices discovered by libusb_get_device_list. If
106 is set to 1 all devices are unref one time.
111 .Fn libusb_get_bus_number "libusb_device *dev"
112 Returns the number of the bus contained by the device
118 .Fn libusb_get_device_address "libusb_device *dev"
119 Return the device_address contained by the device
125 .Fn libusb_get_max_packet_size "libusb_device *dev" "unsigned char endpoint"
126 Return the wMaxPacketSize value on success, LIBUSB_ERROR_NOT_FOUND if the
127 endpoint does not exist and LIBUSB_ERROR_OTHERS on other failure.
132 .Fn libusb_ref_device "libusb_device *dev"
133 Increment the reference counter of the device
139 .Fn libusb_unref_device "libusb_device *dev"
140 Decrement the reference counter of the device
146 .Fn libusb_open "libusb_device *dev" "libusb_device_handle **devh"
147 Open a device and obtain a device_handle. Return 0 on success,
148 LIBUSB_ERROR_NO_MEM on memory allocation problem, LIBUSB_ERROR_ACCESS
149 on permission problem, LIBUSB_ERROR_NO_DEVICE if the device has been
150 disconnected and a LIBUSB_ERROR code on error.
154 .Ft libusb_device_handle *
155 .Fn libusb_open_device_with_vid_pid "libusb_context *ctx" "uint16_t vid" "uint16_t pid"
156 Convenience function to open a device with is
160 Return NULL on error.
165 .Fn libusb_close "libusb_device_handle *devh"
166 Close a device handle.
171 .Fn libusb_get_device(libusb_device_handle *devh)
172 Get the device contained by devh. Return NULL on error.
177 .Fn libusb_get_configuration "libusb_device_handle *devh" "int *config"
178 Return the bConfiguration value of the current configuration. return 0
179 on success, LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
180 and a LIBUSB_ERROR code on error.
185 .Fn libusb_set_configuration "libusb_device_handle *devh" "int config"
186 Set the active configuration
188 for the device contained by
190 This function return 0 on success, LIBUSB_ERROR_NOT_FOUND if the requested
191 configuration does not exist, LIBUSB_ERROR_BUSY if the interfaces are currently
192 claimed, LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and a
193 LIBUSB_ERROR code on failure.
198 .Fn libusb_claim_interface "libusb_device_handle *devh" "int interface_number"
199 Claim an interface in a given libusb_handle
201 This is a non-blocking function. It return 0 success, LIBUSB_ERROR_NOT_FOUND
202 if the requested interface does not exist, LIBUSB_ERROR_BUSY if a program or
203 driver has claimed the interface, LIBUSB_ERROR_NO_DEVICE if the device has
204 been disconnected and a LIBUSB_ERROR code on failure.
209 .Fn libusb_release_interface "libusb_device_handle *devh" "int interface_number"
210 This function release an interface. All the claimed interface must be released
211 before closing a device. Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if the
212 interface was not claimed, LIBUSB_ERROR_NO_DEVICE if the device has been
213 disconnected and LIBUSB_ERROR on failure.
218 .Fn libusb_set_interface_alt_setting "libusb_device_handle *dev" "int interface_number" "int alternate_setting"
219 Activate an alternate setting for an interface. Returns 0 on success,
220 LIBUSB_ERROR_NOT_FOUND if the interface was not claimed or the requested
221 setting does not exist, LIBUSB_ERROR_NO_DEVICE if the device has been
222 disconnected and LIBUSB_ERROR code on failure.
227 .Fn libusb_clear_halt "libusb_device_handle *devh" "unsigned char endpoint"
228 Clear an halt/stall for a endpoint. Returns 0 on success, LIBUSB_ERROR_NOT_FOUND
229 if the endpoint does not exist, LIBUSB_ERROR_NO_DEVICE if the device has been
230 disconnected and a LIBUSB_ERROR code on failure.
235 .Fn libusb_reset_device "libusb_device_handle *devh"
236 Perform an USB port reset for an usb device. Returns 0 on success,
237 LIBUSB_ERROR_NOT_FOUND if re-enumeration is required or if the device has
238 been disconnected and a LIBUSB_ERROR code on failure.
243 .Fn libusb_check_connected "libusb_device_handle *devh"
244 Test if USB device is still connected. Returns 0 on success,
245 LIBUSB_ERROR_NO_DEVICE if has been disconnected and a LIBUSB_ERROR
251 .Fn libusb_kernel_driver_active "libusb_device_handle *devh" "int interface"
252 Determine if a driver is active on a interface. Returns 0 if no kernel driver
253 is active, returns 1 if a kernel driver is active, returns LIBUSB_ERROR_NO_DEVICE
254 if the device has been disconnected and return a LIBUSB_ERROR code on failure.
259 .Fn libusb_get_driver "libusb_device_handle *devh" "int interface" "char *name" "int namelen"
262 .Fn libusb_get_driver_np "libusb_device_handle *devh" "int interface" "char *name" "int namelen"
263 Gets the name of the driver attached to the given
267 into the buffer given by
271 Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if no kernel driver is attached
272 to the given interface and LIBUSB_ERROR_INVALID_PARAM if the interface does
274 This function is non-portable.
275 The buffer pointed to by
277 is only zero terminated on success.
282 .Fn libusb_detach_kernel_driver "libusb_device_handle *devh" "int interface"
285 .Fn libusb_detach_kernel_driver_np "libusb_device_handle *devh" "int interface"
286 Detach a kernel driver from an interface.
287 This is needed to claim an interface required by a kernel driver.
288 Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if no kernel driver was active,
289 LIBUSB_ERROR_INVALID_PARAM if the interface does not exist, LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and a LIBUSB_ERROR code on failure. This function is non-portable.
294 .Fn libusb_attach_kernel_driver "libusb_device_handle *devh" "int interface"
295 Re-attach an interface kernel driver previously detached. Returns 0 on success,
296 LIBUSB_ERROR_INVALID_PARAM if the interface does not exist, LIBUSB_ERROR_NO_DEVICE
297 if the device has been disconnect, LIBUSB_ERROR_BUSY if the driver cannot be
298 attached because the interface is claimed by a program or driver and a
299 LIBUSB_ERROR code on failure.
308 .Fn libusb_get_device_descriptor "libusb_device *dev" "libusb_device_descriptor *desc"
309 Get the USB device descriptor for the device
311 This is a non-blocking function. Returns 0 on success and a LIBUSB_ERROR code on
316 .Fn libsub_get_active_config_descriptor "libusb_device *dev" "struct libusb_config_descriptor **config"
317 Get the USB configuration descriptor for the active configuration. Returns 0 on
318 success, returns LIBUSB_ERROR_NOT_FOUND if the device is in unconfigured state
319 and return another LIBUSB_ERROR code on error.
323 .Fn libusb_get_config_descriptor "libusb_device *dev" "uint8_t config_index" "libusb_config_descriptor **config"
324 Get USB configuration descriptor based on its index
326 Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if the configuration does not exist
327 and returns another LIBUSB_ERROR code on error.
331 .Fn libusb_get_config_descriptor_by_value "libusb_device *dev" "uint8 bConfigurationValue" "libusb_config_descriptor **config"
332 Get a USB configuration descriptor with a specific bConfigurationValue. This is
333 a non-blocking function which does not send request through the device. Returns 0
334 on success, LIBUSB_ERROR_NOT_FOUND if the configuration does not exist and another
335 LIBUSB_ERROR code on failure.
339 .Fn libusb_free_config_descriptor "libusb_config_descriptor *config"
340 Free a configuration descriptor.
344 .Fn libusb_get_string_descriptor_ascii "libusb_device_handle *devh" "uint8_t desc_idx" "unsigned char *data" "int length"
345 Retrieve a string descriptor in C style ascii. Returns a number of byte on success
346 and a LIBUSB_ERROR code on failure.
350 .Sh USB ASYNCHRONOUS I/O
353 .Ft struct libusb_transfer *
354 .Fn libusb_alloc_transfer "int iso_packets"
355 Allocate a transfer with
357 numbers of isochronous packet descriptors. Returns NULL on error.
361 .Fn libusb_free_transfer "struct libusb_transfer *tr"
366 .Fn libusb_submit_transfer "struct libusb_transfer *tr"
367 This function will submit a transfer and returns immediately. Returns 0 on
368 success, LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and
369 LIBUSB_ERROR code on other failure.
373 .Fn libusb_cancel_transfer "struct libusb_transfer *tr"
374 This function asynchronously cancel a transfer. Returns 0 on success and
375 LIBUSB_ERROR code on failure.
378 .Sh USB SYNCHRONOUS I/O
382 .Fn libusb_control_transfer "libusb_device_handle *devh" "uint8_t bmRequestType" "uint8_t bRequest" "uint16_t wValue" "uint16_t wIndex" "unsigned char *data" "uint16_t wLength" "unsigned int timeout"
383 Perform a USB control transfer. Returns the actual number of bytes
384 transferred on success in the range from and including zero until and
387 On error a libusb error code is returned, for example
388 LIBUSB_ERROR_TIMEOUT if the transfer timeout, LIBUSB_ERROR_PIPE if the
389 control request was not supported, LIBUSB_ERROR_NO_DEVICE if the
390 device has been disconnected or another LIBUSB_ERROR code on other failures.
391 The libusb error codes are always negative.
395 .Fn libusb_bulk_transfer "struct libusb_device_handle *devh" "unsigned char endpoint" "unsigned char *data" "int length" "int *transferred" "unsigned int timeout"
396 Perform an USB bulk transfer.
397 A timeout value of zero means no timeout.
398 The timeout value is given in milliseconds.
399 Returns 0 on success, LIBUSB_ERROR_TIMEOUT
400 if the transfer timeout, LIBUSB_ERROR_PIPE if the control request was not
401 supported, LIBUSB_ERROR_OVERFLOW if the device offered more data,
402 LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and
403 LIBUSB_ERROR code on other failure.
407 .Fn libusb_interrupt_transfer "struct libusb_device_handle *devh" "unsigned char endpoint" "unsigned char *data" "int length" "int *transferred" "unsigned int timeout"
408 Perform an USB Interrupt transfer.
409 A timeout value of zero means no timeout.
410 The timeout value is given in milliseconds.
411 Returns 0 on success, LIBUSB_ERROR_TIMEOUT
412 if the transfer timeout, LIBUSB_ERROR_PIPE if the control request was not
413 supported, LIBUSB_ERROR_OVERFLOW if the device offered more data,
414 LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and
415 LIBUSB_ERROR code on other failure.
422 .Fn libusb_try_lock_events "libusb_context *ctx"
423 Try to acquire the event handling lock. Returns 0 if the lock was obtained and 1
428 .Fn libusb_lock_events "libusb_context *ctx"
429 Acquire the event handling lock. This function is blocking.
433 .Fn libusb_unlock_events "libusb_context *ctx"
434 Release the event handling lock. This will wake up any thread blocked
435 on libusb_wait_for_event().
439 .Fn libusb_event_handling_ok "libusb_context *ctx"
440 Determine if it still OK for this thread to be doing event handling. Returns 1
441 if event handling can start or continue. Returns 0 if this thread must give up
446 .Fn libusb_event_handler_active "libusb_context *ctx"
447 Determine if an active thread is handling events. Returns 1 if yes and 0 if there
448 are no threads currently handling events.
452 .Fn libusb_lock_event_waiters "libusb_context *ctx"
453 Acquire the event_waiters lock. This lock is designed to be obtained under the
454 situation where you want to be aware when events are completed, but some other
455 thread is event handling so calling libusb_handle_events() is not allowed.
459 .Fn libusb_unlock_event_waiters "libusb_context *ctx"
460 Release the event_waiters lock.
464 .Fn libusb_wait_for_event "libusb_context *ctx" "struct timeval *tv"
465 Wait for another thread to signal completion of an event. Must be called
466 with the event waiters lock held, see libusb_lock_event_waiters(). This will
467 block until the timeout expires or a transfer completes or a thread releases
468 the event handling lock through libusb_unlock_events(). Returns 0 after a
469 transfer completes or another thread stops event handling, returns 1 if the
474 .Fn libusb_handle_events_timeout "libusb_context *ctx" "struct timeval *tv"
475 Handle any pending events by checking if timeouts have expired and by
476 checking the set of file descriptors for activity. Returns 0 on success, or a
477 LIBUSB_ERROR code on failure.
481 .Fn libusb_handle_events "libusb_context *ctx"
482 Handle any pending events in blocking mode with a sensible timeout. Returns 0
483 on success, returns a LIBUSB_ERROR code on failure.
487 .Fn libusb_handle_events_locked "libusb_context *ctx" "struct timeval *tv"
488 Handle any pending events by polling file desciptors, without checking if
489 another threads are already doing so. Must be called with the event lock held.
493 .Fn libusb_get_next_timeout "libusb_context *ctx" "struct timeval *tv"
494 Determine the next internal timeout that libusb needs to handle. Returns 0
495 if there are no pending timeouts, 1 if a timeout was returned, or LIBUSB_ERROR
500 .Fn libusb_set_pollfd_notifiers "libusb_context *ctx" "libusb_pollfd_added_cb added_cb" "libusb_pollfd_removed_cb remove_cb" "void *user_data"
501 Register notification functions for file descriptor additions/removals.
502 These functions will be invoked for every new or removed file descriptor
503 that libusb uses as an event source.
506 .Ft const struct libusb_pollfd **
507 .Fn libusb_get_pollfds "libusb_context *ctx"
508 Retrive a list of file descriptors that should be polled by your main loop as
509 libusb event sources. Returns a NULL-terminated list on success or NULL on failure.
511 .Sh LIBUSB VERSION 0.1 COMPATIBILITY
513 The library is also compliant with LibUSB version 0.1.12.
518 .Fn usb_get_string_simple
519 .Fn usb_get_descriptor_by_endpoint
520 .Fn usb_get_descriptor
521 .Fn usb_parse_descriptor
522 .Fn usb_parse_configuration
523 .Fn usb_destroy_configuration
524 .Fn usb_fetch_and_parse_descriptors
527 .Fn usb_interrupt_write
528 .Fn usb_interrupt_read
530 .Fn usb_set_configuration
531 .Fn usb_claim_interface
532 .Fn usb_release_interface
533 .Fn usb_set_altinterface
544 .Fn usb_check_connected
551 .Pa http://libusb.sourceforge.net/
556 support first appeared in